House-heating system



Filed Dec. 18, 1925 gig i g Q Patented Dec. 30, 1930 UNITED- STATES- HENRY L. IDOHEBTY, or NEW YORK, NY.

HOUSE-HEATING SYSTEM Application filed December 18, 1925. Serial No. 76,152.

This invention relates to a method and apparatus which shall provide for heat requirements in gas-burning heating systems at such times as gas may not be available or the supply thereof be limited.

Regardless of the particular manner in which gas may be metered to the consumer, it not infrequently happens during periods of unusually cold weather that the flow of gas is insuflicient to meet the consumers requirements,-the reduction in flow being occasioned by the great general demand for gas at such periods. Gas is sometimes metered to the consumer in such a manner that only a limited amount of gas can be taken from the mains at any given time. \Vhen such is the case, the consumer must choose as to which of his gas burning appliances shall have first call on the available supply. For example, as between a kitchen range and a house heating furnace, the former would be given the preference and the furnace fired by some other kind of fuel while the preferred appliance is consuming the available supply of gas.

The present invention aims to provide an oil burning system in connection with a gasfired heating appliance, such as a .househeating furnace, and to so correlate the same therewith that the oil burning system will automatically function when the gas supply to the furnace is not sufiicient to satisfy the heat requirements.

Another aim or object of the invention is to make the oil burning system subject to control by theoutside or weather temperature preferably in such a manner that the oil burning system will be put into active operation in advance of the immediate heat requirements of the home being heated when the outside temperature falls to a predetermined point.

Another object is to provide a house heating system which shall be mutually advantageous to the gas company as well as to the consumer. To this end the invention provides a house-heating system adapted to utilize gas as the base or normal fuel and oil as a supplementary fuel whereby the consumer obtains the advantages of a base fuel of high-heating-value and which moreover is clean, easily burned, and for which no storage provision need he made bythe consumer, advantages which obviously appeal Very greatly to the consumer. and whereby the gas company supplying the gas will not be called upon to provide gas-storage equipment or gas-making equipment greatly in excess of the normal load requirements or in other words equipment which would be called into use only to satisfy unusual peak load requirements, requirements which wouldput an undue burden of expense on the company and result in increased costof the gas.

Thevarious novel features of the invention and additional objects of the same will more fully appear from the detailed description taken in connection withthe accompanying drawings forming part of this specification.

Fig. l of the drawings is a diagrammatic representation of a combined gas and oil burning system embodying apparatus elem'cnts suitable for carrying out the method of the present invention;

Fig. 2 is an end elevation on an enlarged scale of the rotary switch J shown in side elevation in Fig. 1.

The gas consuming appliance having first calP on the gas supply has been indicated as a kitchen range 10 and the gas consuming appliance having secondary call on the supplyas a house heating furnace 11. The furnace is provided with any suitable gas burner 12, an oil burner 13, and a pilot burner 14. Leading from the gas burner 12 is a conduit or pipe 15 at the free end of which is a g'as- 80 air mixing chamber 16, the flow of gas and air to which is controlled by any suitable device as by the combined needle and cover wardly from below the firebox chamber in which the oil and as burners are mounted.

In order that t e requisite amount of secondary air may be supplied to the oil burner when the same is operating, the air ox is perovided with damper 31 which is adapted to opened by the pressure of the primary air supplied by the blower 26. The damperoperating means may-fbe of any preferred form but as shown, there is provided a cylinder 32 within which is a piston 33, a pipe 34 connecting the cylinder 32 with the primary! air pipe 24. The damper is provided wit 'a lever arm 35 to the free end of which the piston 33 is connected by a piston rod. As the air pressure in the primary air pipe 24 builds up, the piston 33 will be moved to open the damper 31 as will be readily understood.

The gas and oil'burning systems above described are under the control of a room thermostat R. Included in the room thermostat control system. is a motor, H so conof gas to the gas burner and also to cut ofl;'

the flow of oil' to the oil burner in case oil and gas are being burned at the sametime.

The means for shutting OR the gas supply upon actuation of the motor may be of any approved form. As shown, however, the shaft 36 ofthe motor H is provided with a cam 37 which is adapted to move a bar 38- pivoted on a standard 39. ,An elbow lever 40 is pivoted between he ends on a suitable support 42. One-end of the 'lever'is connected as at 44 with'thecover valve 18 of the air gas mixing device andothe other end is connected to the bar 38by 'means of a link 46.

- In order to.op en the air box 30 to the atmos- 'phere when gas is being burned there is provided a damper 48 which is adapted to be opened when the motor H is actuated to per-' mit gas to flow to the gas burner. The damper 48 is conveniently connected bymeans of -a link 49 with the elbow lever 40 whereby movement will be imparted to the damper at the. same time that movement is imparted to the air and gas controlling valves 18 and 17, res actively.

hen the motor H is actuaged to shut off the gas supply it also interrupts the continuity of a power line 50- -52 between the combined pump and blower motor 28 and the main. .power circuit 51-, thus-preventing motor 28.

from running. This break in the power line I 50-52 ma be effected in any desired manner as by a switch J (see Figs. 1 and 2) mounted.

on shaft 36 outside the casing of the motor H disposed between the adjacent terminals 53' of said power circuit. The switch J is so arranged that when shaft 36 is in one position of rest, one side 500i the power circuit leading to the pump motor 28 is closed, and when it is in itsother position-ofrest said power circuit is open. Essentially the switch J (see Fig. 2) comprises a 90 segment of conducting material placed in a non-conducting disc aflixed to the end of the motor shaft 36, brushes 53 being providedat the ends of the adjacent terminals of the circuit 50 for o erative engagement with the rotary switch.

he other wire of the power circuit of motor 28 is indicated in part at 54, the same leading to a normally close'dswitch in a-boiler thermostat B. A wire 55 connects the thermostat B with one side of a normally open switch G. From switch G the circuit runs through wire 56 to the power circuit 51. The motor H is connected to the power circuit 51 by wires 52 and 57 The room thereinostat Rhas two fixed con- 1 tacts 58 and 59 between which operates the movable element 60. Contacts 58 and 59 lead direct to the motor H through wires 62 and 64 respectively, said wires passing through a j unction box 66. The movable element 60 of .the thermostat is also connected to motor Hby way of wire 68, 70 and ,71. Between wire 68 and 70 is a thermostat P which normally keeps the circuit through said wires closed when the pilot 14 is burning. 7 When the room thermostat R is in a no-callfor-heat position, the movable element 60 will have moved to the right and closed the circuit. between wires 64'and 7.1. The motor H willtherefore be actuated to shut 0a the flow of gas to the burner 12 and to breakthe power circuit 50-52 of the oil pumping motor 28 by opening switch J. When theroom thermostat R is in a call-for-heat position. the movable element will have moved to the left'and closed the circuit'between wires 62 and 71.. The motor H will therefore be actuated to start the flow' of gas to the burner 12 and to close the power circuit 50-52 of the oil pump 28 at switch J, whereupon if the pump motor circuit is otherwise complete it will be actuated to supply air and oil to theoil burner 13. v

The pilot thermostat P is so constructed that upon accidental extinguishment of the."

pilot light the circuit 64 71 will be closed whe ri eby to actuate the motor H to shut off the close the circuit between wire 64 and 71 with the result that the motor H will be actuated to prevent the flow of fuel to the burners.

' The boilergovernor thermostat B is set to ow of gas to the gas burner and to breakthe power circuit 50-52 of the motor- 28 at switch J. To this end the pilot thermostat P is provided with wire 72 which taken with wire 70 provides a circuit which will.

break the power circuit (which includes wire 54) leading to the motor 28 when the temperature. of the boiler reaches a maximum safety limit.

Connected in parallel across the normally open switch G are two normally open switches L and T. One side of the switch L has a wire 72-) connecting with the wire 56 which leads from the power circuit 51 to switch G. The other side of the switch is connected by'a wire Tl to one side of the boiler thermostat B. One side of the switch T also connects with Wire 56 through wire 75 and the other side con nccts with wire 74 (and hence to the boiler thermostat B) through wire 76.

The switch T is controlled by a thermostat O on the outside of the house, a. wall of which is shown at 84. The thermostat may be of any suitable type but has been shown as of the pneumatic type. A tube 77 leads from the thermostat proper to a cylinder 78 within which is a piston 79. This piston is appropriatcly connected with a movable element 80 of the switch T, said element being shown as a mercury tipping switch. When the outside temperature falls to a predetermined point,.themovable element 80 of the switch is actuated to close the circuit between wires 75 and 76. lVhen the circuit 75-76 is closed the circuit between wire 56 (through wire 74) and wire 54 will be closed. It now power circuit 50-52 is closed the motor 28 will be actuated as will be readily understood. It

' will be remembered that it tlIO thQIITIOStQIt R is in a call-tor-heat position the circuit 52 of motor 28 will be. closed. Under these conditions the oil burning system will be put into active operation even though the furnace is being supplied wit-h gas. The switch T therefore operates to put the oil burning system into active operation in advance of the anticipated reduction of supply.

The gas supply main is indicated at 82 and leads to a com'entioual volume meter 86 from whence the gas flows by way of a pipe 88 to a flow. limiting device generally indicated at 90. vice 90 is a pipe 91 which divides into two branches 92 and 9;). Branch 92 leads to the kitchen range 10 andbranch 93 leads to a special type of valve 94; hereinafter more fully referred to and through which the gas must pass before flowing to the furnace gas burner 12 through the pipe. 19. Continued as a branch from the pipe 93 is a pipe'95 which leads to the pilot 14.

The switch L is adapted to be operated by a. pressure-responsive device shown as a diaphragm 96, one side of which is'connected by a pipe 97 to the gas main 82 on the inlet side of the volume meter 86. When the pressure in a supply main 82 falls below a predetermined point the switch I will be closed. Upon the switch L being closed, the circuit to motor 28 will be closed along one line therehcrcwed into the outlet side of said deof, namely, between wires 56 (through 74) and 54 and consequently the motor 28 will be free to operate to put the oil burning syscall-for-heat position.

The valve 94 interposed betwccnthe gas pipes 19 and 93- is so constructed that the flow of gas will be cut oil' when the pressure in the line between said valve 94 and the flow limiting device 90 falls to a predetermined point. The valve 94 may be of any preferred construction but as shown it consists of a weighted diaphragm 98 which controls a flow passage. \Vhenthe gas pressure in the line 93 is suliiciently high it will raise. the diaphragm ofl' its seat and permit gas to flow into the pipe 19 on the outlet side of said Valve.

W' hen the gas pressure in the line 93 is not sufi'iciently high to raise the diaphragm, means are provided for closing one side of the power circuit to the oil pump motor 28 so that if the room thermostatR is in a call-for-heat position the heat requirements may be. met by the burning of oil in the furnace. The means for closing said circuit has been shown as including a diaphragm 99 which on one. side is subject to the pressure of the gas in the line 93 leading to the. valve SH and which on its other side is subject to the pressure existing within the pipe 19 on the outlet side of the valve 94. A pipe 100 leads from the top'of the diaphragm to the 'pipe 93 and a pipe 101 leads from the under ed orifice ($1 from whence it flows to the outlet pipe 91. W'ithin the device is a weighted diaphragm (33, the under side of which is subject to the pressure of the outgoing gas by way of a port 65 and an opening 67 in a wall below the diaphragm. Depending from the diaphragm and extending through the opening (37 is a stem (39 to the lower end of which is secured a valve 81 adapted to shut olt the flow of gas to the orifice 61 such closure being affected when the pressure of the gas on-the outlet side of the. orifice is high enough to elevate the diaphragm (53. Secured to the top of the diaphragm is a post 83 to which is attached one end of a wire 85 which leads to the. wire H which in turn leads to the motor 28 through wire. 54. The post is adapted to make contact with theterminal of a wire 87 which is connected to the wire 56 which leads from the power circuit 51. The switch in the pipe line 97 leading to the diaphragmbetween the wires 85 and 87 ma forconvenience of description beterme switch F and may be of any preferred form. lVhen the pressure of the gas on the outlet side of: the orifice 61 falls below a predetermined point, the diaphragm 63 will move downwardly a suflicient distance to. close the switch F. When the switch F is closed one side of the power circuit leading to motor28 will be closed and hence if the room thermostat R is in a call-for-heat position the motor 28 will be put into operation with the result that oil burning system will be put into operation.

The interior mechanism of the flow limiting device 90 also includes a die? hragm 89 the upper side of which is sub ect to the same gas pressure as the under side of the diaphragm 63, namely, the pressure of the gas which has passed through the orifice 61. The under side of diaphragm 89is subject to the pressure of the incoming gas. The valve stem 69 passes through a central opening in the diaphragm 89 in such a manner.

that under certain conditions of operation relative movement may be had between the diaphragm 89 and the valve stem 69. In order to enable the valve stem to be moved upwardly by the diaphragm 89 the valve stem is conveniently provided with a shoulder or abutment above the diaphragm 89.

The mode of operation of the flow limiting device 90 is such that only a-limited amount of gas can be taken. from the supply main 82. The customer will usually have the device 90 so regulated that enough gas can always be obtained to satisfy the maximum requirements of the primary gas consuming appliances such as the kitchen range. If gas should be flowing to the furnacell at the time it is desired to operate" the kitchen range 10 or .other primary gas consuming ap liances, the

valve 94 will operate to close 0 the flow of gas to the furnace burner 12 when the pressure of the gas in the line 93 leading to said valve 94 falls below a predetermined point.

In order that the house may not suffer for lack of heat during such time as the supply of gas to the furnace gas burner 12 is cut off and the room thermostat R is in a call-forheat position, the switch G associated with the valve 94 will close the circuit to the motor 28 whereupon the oil burning system will. he put into operation.

In order that the circuit-controlling diaphragms 96 and 99 may not be too sensitive to slight variations in pressure, suitable means for causing a lag in the 0 eration of the diaphragms may be provide 2 Such means may conveniently take the form of restrictions in the pipe lines leading to the diaphragms, the restrictions preferably being arranged in relatively, smallreceivers or chambers in which the gas passing through i the restrictions enters. I

Referring to the drawings, the restriction 96 is indicated at 96 and its receiver at '97. The restriction in the pipe line 100 leading to the upper side of the diaphragm 99 is indicated at 99 and its receiver at 100. The restriction in the pipe line 101 leading to the bottom of the diaphragm is indicated at 102 and its receiver at 103. a

It will-be noted that the weather subject thermostat O is so connected to the oil burning apparatus that it will function to put said apparatus into active operation irrespective of the type of device or means through which gas is supplied to the furnace. As regards the broad idea of weather control of the oil burning system, the gas pipe '88 leading fromthe volume meter 86 could just as'well lead.

directly to the gas-air mixer,16 or in other words tothe gas burner 12 and the same is true as regards the control exercised on the oil burning system by the switch L which is subject to the control of the gas pressure in the main 82. That is to say, as regards thesetwo controlling means the demand limiting device 90 and the cut-off valve 94 could just as well be omitted. It is, however, preferred to employ the cut-off valve 94 in connection with the gas-main-pressure responsive device 96 and to ,set said device 96 for actuation of the oil burning system at a pressure higherthan the low point pressure which will causethe cut-off valve 94 to function. The pressure responsive device 96 will, therefore, set the oil burning system into'operation'or make it ready for operation before the reduction in gas main pressure makes itself felt at the cut-off valve 94 andconse uently the-device 96 is to this extent indepen ent of valve falls below a predetermined point I whereby the available supply of gas to which the customer is entitled by the demand limiting device in conserved for other uses. While the cut-off valve 94 will operate to cut off the flow of gas to the furnace when a certain predetermined low pressure obtains between the demand limiting device 90 and said valve I whereby to conserve the available supply of gas for use in the primary gas app iances,

the valve 94 performs an additional function which is that it will function to cut off the flow of gas to the furnace when the gas pres sure in the gas main 82 falls to a predeter- -mined low point thereby making available for'o'ther than furnace purpose the supply of gas in. the gas system as a whole between the gas plant and the individual consumers being supplied with gas. In view of the fact that the cut-ofi valve 94 will cut off the flow I volume meter 86.

I is that it limits the amount of gas which a three distinct temperature points.

customer is entitled tense in a given period of time, but the omitting of the demand limiting device with its consequent function would not in any'manner interfere with the operation of the cut-otf valve 94 as regards its function of cutting off the flow of gas to the furnace when the gas pressure on its inlet side falls below a predetermined point.

\Vhcn the switch G is operated due to the cut-off of the flow of gas to the furnace by the valve 94, the oil burning system comes into operation to burn oil in place of gas in the furnace. The switch L on the other hand when operated by the gas pressure in the gas main will put the oil burning system into operation irrespective of whether or not gas is being supplied and burned in the furnace and consequently oil and gas may be burning at the same time and until such time as the pressure in the gas main 82 falls low enough to cause the valve 94 to cut off further flow of gas to the furnace,

It is of course understood that as between the weather-subject thermostat O and the rooi11-temperattire-controlled thermostat R,

. the latter is the master control of the entire system. Considering for the moment one phase of the relationship between the two said thermostats. it will of course be understood that thermostat It operates between two predetermined temperature points, namely,

the maximum and minimum dsirableroom temperatures, and that thermostat O oper-' ates at a temperature which is below-usuall'y very considerably belowthe minimum desirable room temperature. Said thermostatic control system 1 involves, therefore, It will also be remembered that the control exercised by thermostat O is effective even though the furnace gas burner 12 is being furnished with a full supply of gas. It will now be apparent that the thermostat Q will function to put the oil burning system into operation or to make it ready for operation if thermostat R is in a call-for-heat position provided the thermostat O is subject to a t mperature low enough to cause it to operate the switch T.

It will be understood from the foregoing description that gas is the base or primary fuel normally relied upon to satisfy the fuel requirements of the furnace; that the oil burning system is provided to take care of the fuel requirements when the gas supply is not sufiicient for that purpose; that the oil burning system is so controlled that it will come into active operation when the weather temperature falls toa certain low degree even though gas may at the time be flowing to the furnace; that it will come into active operation when the gas-pressure in the main falls below a predetermined point; that it will come into active operation when the gas supply to the furnace has been cut off and that I it will come into active operation depending on certain conditions existing in a device for limiting the flow of gas from the gas main.

\Vhile the invention has been described with considerable particularity of detail it is to be undeistood that no limitations are intended except as may be defined by the appended claims.

What is claimed is:

1. The combination ofmeans for supplying the fuel requirements of a house heating system, comprising a gas burning system adapted to supply the fuel requirements of the furnace as long as the pressure on the gas being supplied to the system is maintained at a given pressure, an oil burning system, and electrically operable means under the control of said gas pressure for putting the oil burning system into active operation to supply fuel oil to the furnace when the gas pressure falls to a predetermined point.

2. The combination specified claim 1, and means for cutting off the flow of gas to the furnace when the gas pressure falls to a predetermined point.

'3. The combination of means for supplying the fuel requirements of-a house heating system, comprising a gas burning system adapted to operate on a continuously limited supply of gas which is sufficient to satisfy the fuel requirements of the furnace as long as said supply is available at a given mini mum pressure, an oil burning system, and means for cutting off the supply of gas to the furnace when the gas pressure of the avail able limited supply is less than said given minimum pressure, and for puttlng the oil burnin s stem into active 0 oration to su ply fuel oil to the furnace when said gas supply has been cut off.

4. The combination of means for supplying the fuel requirements of a house heating system, comprising a gas burning system adapted to supply the fuel requirements of the furnace as long as the pressure on the gasbeing supplied to the system is maintained at a. given pressure, an oil burning system and a thermostat subject to weather temperature adapted to put the oil burning system I 6. A method of operating a house heating furnace provided with means for burning gas and oil, wherein the gas pressure is a co'ntrolling medium for the oil burnmg system,

furnace when the gas pressure falls below said predetermined minimum.

furnace provided with means for burning gas andoil, comprising burning gas in the furnace as lon as the gas pressure remains above a pre etermined minimum, automatically shutting oif the flow of gas to the fur nace when the gas pressure falls below said predetermined minimum and burning oil in lace of as while the gas pressure remains low sai predetermined minimum.

8. A method of operating a house heating furnace provided with means for burning gas and oil, comprising burning gas in the furnace as long as the gas pressure remains above a predetermined minimum, and auto,- matically; cuttin off the gas and burning oil in the furnace w en the weather temperature falls to a predetermined-degree.

9; In combination, a house heating furnace equipped with a gas burner and an oil burner, means permitting gas to flow tovthe gas burner only as long as the gas pressure remains above a predetermined minimum, mechanism adapted to feed oil to the oil burner, and ap- 5 paratus controlled by said means for setting said mechanism into operation to feed oilto the oil burner when'the gas pressure falls below said predetermined minimum.

10. In combination, a house heating fur nace equipped with a gas burner and an oil 'burner, a device permitting gas to flow to the gas burner as long as the gas pressure remains above a predetermined minimum, mechanism adapted 'to feed oil .to the oil burner, pressureresponsive means associated with said device,and means controlled by the pressure-responsive means for setting said mechanism into operation to feed oil to the oil burner when a predetermined differential pressure exists on said pressure-responsive means. M I

1.1. In combination, a house heating furnace equipped with a gas burner and an oil burner,'a device permitting gas to flow to the 5; burneronly as long as the gas pressure is above apredtermined minimum, mechanism adapted to feed oil to the oil burner; means controlled by said device for setting said mechanism into operation to feed oil to the co {Oil burner when the gas pressure is belowsaid predetermined and for rendering sald mechanism inoperative when the gas pressure is greater than said minimum.

12.. Incombination, a house heating furwith agas pnrnenandanoil comprising burning gas in the furnace as- 7. A method of operating a house heating burner, a device permitting gas to flow to the gas burner as long as the gas pressure rcmainsabove a predetermined point, mecha- Y nism adapted to feed oil to the .;oil burner, a thermostat adapted to move to call-for-heat. and no-call-fonheat positions, and means controlled by said device for. setting said mechanism .into 0 ration to feed oil to' the burner when the evice has cut off the flow of gas to the gas burner and when the gas pressure falls below said given pressure,

a thermostat subject to weather temperature, and means subject to the control of said thermo'stat adapted to set saidmechanism into operation independently of said device when the weather temperature falls to a predetermined point. I

14. In combination, 'a house heating furnace equippedwith a gas burner and an oil burner, a supply main for supplying gas to the gas burner including gas pressure responsive means for limitlng the amount of gas which can be withdrawn from the supply main during any given period of time, mechanism adapted to feed oil to the oil burner, a device responsive-to the pressure of as in the supplymain, and means controlle by said device for setting said mechanism into opera tion to feed oil to the oil burner when the gas pressure in the supply main falls below a predetermined point. I I I 15. The combination of means for supplying the fuel requirements of a househeating system, comprising a gas burning system and an oil burning system, means for cutting off the supply of gas when the pressure thereof falls to a predetermined low point, means controlled. by said means for putting the oil burning'system into 0 ration, and means for putting the oil burnmg system into '01)- eratlon upon a, fall in pressure of the gas supply whichis not sufficient to operate the first mentioned means.

16. The combination of means for supply- I a ing the fuel requirements of a househeating system, comprising a gas burning system and an oil burning system, means for cutting eration upon a fall in ressure of thegas supply whichis not su cient to operate the first mentioned means, and a weather con v trolled device for putting the oil burning system into operation at a predetermined degree of out-door tei'nperature irrespective of the pressure of the gas being supplied to the gas burning system. r

17. The combination of means for supplying the fuel requirements of a house heating system comprising a normally functioning gas burning system and a normally nonfuctioning oil burning system, and means subject to the weather temperature for putting the oil burning system into operation at a predetermined weather temperature while the gas burning system is functioning.

18. The combination of means for supplying the fuel requirements of a house heating system comprising a normally functioning gas burning system and a normally nonfut-tioning oil burning system means subject to the weather temperature for putting the oil burning system into operation at a pre determined weather temperature while the burning system is funetionin", and means under the control of the gas supply pressure for cutting out the gas burning system while the oil burning system is functioning and when the. gas pressure falls to a predetermined low point.

19. A method of operating a househeating system using gas as the base fuel and adapt ed to use oil as a secondary fuel, comprising burning gas until the pressure of the gas supply falls below a predetermined point at which the gas supplyis cut off, burning oil along with the gas immediately prior to the fall in thegas pressure to said predetermined point, and continuing to burn oil after said predetermined pressure has been reached.

20. A method of operating a househeating system usinggas as the base fuel and adapted to use oil as a secondary fuel, comprising burning both gas and oil when the weather temperature is at a predetermined low point and discontinuing the burning of oil when the weather temperature rises above said predetermined point while. still continuing to burn gas.

21. In a fluid fuel heating system, the combination of a gas burner, an oil burner, and means responsive to changes in the Weather temperature adapted to place said oil burner in operation when the weather temperature drops below a predetermined low point. L

22.- In a fluid fuel heating system, theconibination of means for burning gas, an oil burner, normally inoperative means for feed in fuel oil tothe oil burner, a thermostat subject to weather temperature, a thermostatsubject to indoor temperature, means under the control of the indoor thermostat adapted to cutoff the flow of gas to the gas burning means when a predetermined temperature has been reached, and means under'the control of the weather-thermostat for making tioning out of operation.

ready the operation of means for feeding oi to the oil burner. J v

23. In a fluid fuel heating system, the coinstat subject to indoor temperature, means under the control of the indoor thermostat adapted to cut off the flow of gas to the gas burning means when a predetermined temperature has been reached, and means under the control of the weather thermostat for making ready the operation of means for feeding oil to the oil burner, the operation of said oil feeding means 'being under the final control of the indoor thermostat.

:24. In a heating system, the combination of a normally functioning fuel burning device, a normally non-functioning fuel burn ing device, and means under the control of the weather temperature for putting. said normally non-functioning fuel burning device into operation.

In a heating systen'ipthe combination of two fuel-burning devices, temperature controlled means for governing the operation of said devices, one of said devices normally functioning as long as a given maximum ten'iperature has not been reached, and the other of said devices normally functioning as lon as a temperature which is substantially below a given minimum temperature prevails. 1

26. In a heating system, the combination of two fuel-burning devices, and temperature operated means for controlling the operation of said devices, said means operating at a given temperature to put at least one of said devices into operation and operating at a lower temperature to'put both of said devices into operation and operating at a given temperature higher than either of said temperatures to put such devices as are func- 27. A method of operating a house heating system provided with two fluid-fuel burning means comprising operating both of said means as long as a given-low temperature prevails, discontinuing the operation of one of said means when a temperature higher than said given low temperature prcrails, and discontinuing the operation of the going of said meaiis when a predetermined temperature higher than either of said temperatures prevails.

28. The combination with a pair of fuelburning devices, of means for supplying fuel thereto from a source of-variable supply and means for shutting off one of said devices in accordance with the reduction in the supply of said fuel. j

29 The combination with a furnace of means for supplying separate fuels thereto and mechanism responsive to the pressure lit) at which one of said fuels is supplied for controlling the supply of one of said fuels.

30. The combination with a steam generating boiler of means for supplying separate fuels thereto and pressure responsive mechanism independent of the pressure of steam generated for controlling the supply of one p of said fuels.

231. The combination with a domesticheating system including-a furnace and a gas burner and an oil burner in said furnace, of a mechanism adapted to feed oil to the oil burner, a device permitting gas to flow to the gas burner whenever the indoor temperature drops below a predetermined point, a

thermostat responsive to changes in outdoor temperature, means controlled by said thermostat for setting said mechanisminto operation to feed oil to the oil burner whenever the outdoor temperature falls below a pre-' determined polnt, a thermostat responsive to changes in indoor temperature, and means subject to the control of said thermostat adapted to throw said mechanism out of 35 operation irrespective of the outdoor tem- I 'perature whenever the indoor temperature exceeds a predetermined point. I

32. The combination with a domestic heating system including a furnace and a gas burner and an oil burner. in said furnace, of

a mechanism adapted to feed oil to the oil burner, a main for supplying gas to the gas burner including a valve, a thermostat responsive to changes in indoor temperature,v

means controlled by said thermostat for opening the valve in saidgas supply main to feed gas to the gas burner whenever the indoor temperature falls below a desired point, a thermostat responsiveto changes in outdoor temperature, means-controlled byv said outdoor thermostat for settirfg said mechanism into operation to feed oil to the oil burner whenever the outdoor temperature falls below a predetermined point, and means 4 subject to the control of said indoor thermostat adapted to cut'ofl the flow of gas to the a gas burner and to throw said mechanism out of operation whenever the indoor temperature rises much above said desired point.

50 In testimony whereof I afiix my signature/ HENRY L. DOI-IERTY'. 

